This invention relates to gas turbine engines, and more particularly to arrangements for cooling the combustor liners of gas turbine engines.
In gas turbine engines energy is supplied by burning fuel in a combustor or combustion chamber. Fuel is supplied through a fuel nozzle at one end of the combustor, mixed with air and burned. The liner of the combustor is heated by radiation from the flame of the burning fuel and by convection as the combustion gases flow along the liner. In order to prevent excessive temperature of the liner it is conventional to provide a flow of relatively cool air along the exterior of the combustor. Further, holes or other passages have been provided in the wall of the combustor liner causing a portion of the cooling air flowing past the exterior of the combustor to be directed as a film along the interior wall of the combustor liner, so that cooling is provided both for the exterior and the interior of the combustor liner.
One arrangement for cooling the interior surface of the combustor liner is to provide a very large number of very small holes drilled in the combustor wall at an angle of about 20.degree. so that air diverted from the exterior of the combustor through these holes is directed along the interior surface of the liner. These holes are laser-drilled and have a diameter of only about 0.02 inch. A very large number of such very small holes are employed in order to provide adequate and uniform cooling air for the interior surface of the liner. In one specific gas turbine engine about 40,000 such holes are drilled. This large number of holes spaced at frequent intervals over the wall of the combustor causes the cooling air to flow as a film over substantially all of the interior surface of the liner providing very effective cooling.
However, there is one serious problem with this approach to combustor liner cooling. Because of the very small size of the holes, dirt particles in the cooling air may plug a significant number of holes, reducing the flow of the cooling air therethrough and providing inadequate and uneven cooling of the interior surface of the combustor liner.
By the present invention, this problem has been greatly reduced. Provision is made for removing from the air, before it reaches these small holes, substantially all of the dirt particles of a size sufficient to constitute a reasonable possibility of plugging the small holes. Thus, by this invention, the possibility of plugging the holes and blocking the passage of cooling air to the interior surface of the combustor liner is greatly reduced and more effective cooling of this surface is provided.
Accordingly, it is an object of this invention to remove dirt particles from the cooling air being supplied to the interior surface of the combustor liner so as to prevent these particles from plugging very small holes provided in the liner wall for passage of cooling air.